In its basic function, a known aircraft nose landing gear is a shock absorber which consists of a landing gear housing and a thrust tube rotatably mounted therein. At the downwardly protruding end of the thrust tube at least one rotatably mounted nose wheel is seated. To be able to rotate the thrust tube during retraction and extension, toggle levers are used to provide a connection between the thrust tube and a rotary steering tube, wherein the rotary steering tube is rotatably mounted in the landing gear housing. A drive motor generates a rotary movement of the rotary steering tube, which is transmitted to the aircraft wheel via the thrust tube. The current steering deflection of the nose landing gear must be fed back to the aircraft system with an accuracy of better than 1.5°.
A known steering angle sensor unit for detecting the current steering deflection on the one hand has a feedback gear wheel which is firmly connected with the rotary steering tube. On the other hand, a reduction gear wheel is provided, which is coupled with a position sensor, in particular an RVDT sensor or a potentiometer, via a shaft. The gear ratio of feedback gear wheel and reduction gear wheel generally is chosen such that the angle of rotation of the sensor and/or potentiometer is limited to 360° also for a maximum steering deflection of the landing gear. This is necessary, in order to realize an absolute steering angle measurement. A disadvantage of the steering angle detection consists in the mechanical coupling between measuring device and measurement object, which can lead to massive wear phenomena on the components contacting each other.
It is the object of the present disclosure to provide the skilled person with an improved apparatus for determining the current steering deflection of an aircraft landing gear, whose component wear is reduced as compared to the known solution.
This object is solved by an apparatus for detecting the steering angle of an aircraft landing gear in particular of the nose landing gear, comprising a measuring scale which can be mounted coaxially around a rotating component and at least one sensor for the contactless detection of the steering angle by means of the measuring scale. Alternative aspects of the present disclosure are subject-matter of the dependent sub-claims.
Accordingly, an apparatus for detecting the steering angle of an aircraft landing gear, in particular a nose landing gear, includes a measuring scale which can be mounted coaxially around a rotating component for steering an aircraft landing gear. Both components accordingly have an identical axis of rotation. The measuring scale serves to identify individual measured values or a sequence of individual measured values of the rotating component. A sensor is arranged at a distance from the measuring scale and detects the measured values depicted on the measuring scale in a contactless manner. Due to the coaxial rotary movement of measuring scale and aircraft landing gear component, the current steering angle of the aircraft landing gear can be measured in a contactless manner by means of the sensor.
It is conceivable that the measuring scale is ring-shaped and guided completely around the circumference of the rotating component. Accordingly, the apparatus provides for an absolute angle determination in a rotation range from 0° to 360°. Particularly, an absolute angle determination can be performed in the range above 360°. In the present disclosure, a mechanical coupling between sensor and measurement object is omitted, whereby wear phenomena inside the measuring arrangement are noticeably reduced. The measurement signal generation of the sensor is effected continuously. Two or more sensors are redundantly arranged relative to each other in one embodiment.
It is conceivable that at least one sensor is a magnetic sensor. The measurement principle is based on a magnetic action principle between measuring scale and magnetic sensor. Particularly, the use of a magnetostrictive sensor is suitable.
The measuring scale is annularly guided around the full circumference of the rotating component and fixed to the same. The ring width may lie in the range between 10 and 50 mm, particularly in the range between 15 and 30 mm.
What is expedient is a spaced arrangement of the at least one sensor relative to the measuring scale in the range between 0.1 and 5 mm, particularly advantageously in the range between 0.1 and 1.5 mm.
In one example aspect of the present disclosure, the measuring scale consists of a magnetic tape which is made of a permanent-magnetic material. The magnetic tape bears a magnetic signature, which is realized by the precise alignment of various magnetic fields on the magnetic tape. The individual magnetic fields are characterized by pole lengths in the range from 0.1 to 5 mm, which are generated by precisely magnetizing the permanent-magnetic material. A special coding feature of the signature identifies a steering angle of 360°, so that a steering deflection above 360° can be output as absolute value.
It is conceivable that the measuring scale includes one or more tracks. The tracks can expediently be combined to a logically linked signature of the measuring scale. The measuring scale accordingly consists of one or more tracks extending parallel to each other, which can be detected in a contactless manner by means of the sensor separately and/or in parallel. It is furthermore conceivable that the sensor includes at least one reading head per track. Conceivable configurations of the single- or multi-track signature of the measuring scale include a single-track incremental track, an incremental track in conjunction with at least one code track, an incremental track in conjunction with a coarse absolute track and the realization of a vernier by means of two or more tracks.
In a further advantageous configuration possibility the apparatus of the present disclosure provides a passive measuring scale. The measuring scale advantageously is ring-shaped and substantially is made of a ferromagnetic material. On the surface of the measuring scale a mechanical structuring is formed to embody the mechanical signature/coding. The configuration of the mechanical signature of the measuring scale can be effected in a single-track or multi-track manner. What is expedient is a helical signature of the measuring scale. (Furthermore, it is conceivable that at least one track of the measuring scale represents a single-periodic sine/cosine signal.) The expansion by one further track advantageously can serve to increase the measurement resolution.
Particularly, at least one correction track is provided. It can be provided that the correction track symbolizes a constant measured value. With reference to the constant measured value deviations and/or measurement errors can be detected and suitable compensation measures can be taken. For example, by means of the correction track an axial displacement of the rotating component can be detected and compensated. The detected deviations of the constant measured value of the correction track are employed for compensation on all further tracks in one embodiment.
In a further advantageous aspect, the use of one or more ferromagnetic gear wheels as measuring scale is provided. The individual gear wheels with a different number of teeth are attached to the rotating component of the aircraft landing gear relative to each other such that a vernier is obtained. The toothing corresponds to the aforementioned mechanical structuring and/or signature.
When using a passive measuring scale, a permanent magnet expediently is provided inside the apparatus. The permanent magnet may be positioned behind the at least one sensor and magnetizes the passive measuring scale.
With the apparatus for detecting the steering angle of an aircraft landing gear in accordance with the present disclosure a measurement accuracy in the range of better than 1.5° can be achieved. Such measurement accuracies are required in particular in aircraft technology. Furthermore, the steering angle detection in the nose landing gear of an aircraft continuously provides a measurement signal for the current steering deflection of the landing gear to the landing gear computer.
The present disclosure furthermore provides an aircraft landing gear, in particular a nose landing gear, in which a mechanical coupling between measurement sensor and measurement object is omitted. This is solved by an aircraft landing gear according to claim 9. Accordingly, an aircraft landing gear, in particular a nose landing gear, provides a rotatably arranged rotary steering tube which is directly or indirectly connected with the landing gear wheel. A rotary movement of the rotary steering tube effects a steering deflection of the landing gear wheel. In accordance with the present disclosure, a measuring arrangement is provided, which permits a contactless detection of the steering angle of the aircraft wheel.
It can be provided that the measuring arrangement provides a measuring scale which is coaxially arranged around the rotary steering tube of the aircraft landing gear. The measuring scale completely extends around the circumference of the rotary steering tube, so that both components have the same axis of rotation. A sensor mounted at a distance from the measuring scale inside the aircraft landing gear detects the steering deflection of the landing gear wheel in a contactless manner with reference to the measuring scale.
The used measuring scale may be fixed to the rotary steering tube of the aircraft landing gear by bonding and/or by shrinking and/or screwing and/or welding.
The present disclosure furthermore relates to a method for detecting the steering angle of an aircraft landing gear. In accordance with the method of the present disclosure, tapping the actual deflection angle of the nose landing gear is effected in a contactless manner. A mechanical coupling of sensor unit and measurement object is omitted. It is conceivable that a continuously generated measurement signal is permanently transmitted to the landing gear computer. With the method of the present disclosure, a measurement resolution in the range from 1° to 1.5° can be achieved.
Advantageously, the actual steering angle of the aircraft landing gear is determined in a contactless manner by means of a magnetostrictive measuring method. Such measuring method relies on the use of magnetic sensors which operate on the basis of a magnetic action principle and detect the current steering deflection of the aircraft landing gear. Particularly, the method of the present disclosure employs an apparatus for detecting the steering angle of an aircraft landing gear as described herein
Further features, details and advantages of the present disclosure will be explained in detail with reference to the embodiments illustrated in the drawings.